Research Updates: The effect of phenobarbital on serum triglyceride concentrations in epileptic dogs

In this cross-sectional study, sera from 57 dogs with epilepsy that had been treated for at least three months with either phenobarbital (group 1, n = 28) or phenobarbital and potassium bromide (group 2, n = 29) were compared with sera from 57 healthy control dogs that matched the epileptic dogs in age, breed, sex, neuter status, and body condition score. Serum triglyceride, cholesterol, phenobarbital, and total thyroxine concentrations were measured, and canine-specific pancreatic lipase immunoreactivity (cPLI) was determined. Owners had withheld food for at least 12 hours before sampling. Nine of the epileptic dogs (16%) had a history of pancreatitis.

Barrak Pressler, DVM, PhD, DACVIM

Fasting serum triglyceride concentrations were significantly higher in both group 1 and group 2 than in the control group; 25% of dogs in group 1 and 41% of dogs in group 2 had fasting serum triglyceride concentrations greater than the reference range established by using the control dogs. Fasting serum triglyceride concentrations did not correlate with either the phenobarbital dose or serum phenobarbital concentration but did correlate with the patient's body condition score (fasting serum triglyceride concentration increased as the body condition score increased). The epileptic dogs with a history of pancreatitis were 2.2 times more likely to be hypertriglyceridemic than were the epileptic dogs without a history of pancreatitis. Serum cholesterol concentrations were not significantly different among the three groups. Increased cPLI was present in 27% (nine of 33) of the epileptic dogs, although none of the dogs had clinical signs of pancreatitis. Finally, serum total thyroxine concentration was negatively correlated to serum phenobarbital concentration.

COMMENTARY

Lipemic serum in dogs is usually due to hypertriglyceridemia. Hypertriglyceridemia in dogs has been associated with obesity, postprandial sampling, pancreatitis, diabetes mellitus, hypothyroidism, hyperadrenocorticism, and cholestatic liver disease. Other causes may include long-term glucocorticoid administration or a high-fat or high-carbohydrate diet.

This study demonstrates that epileptic dogs treated with phenobarbital alone or in combination with potassium bromide are more likely to be hypertriglyceridemic. Hypertriglyceridemia has previously been hypothesized to be a risk factor for developing pancreatitis. Thus, although not answered by this study, epileptic patients with hypertriglyceridemia secondary to treatment should be monitored for development of pancreatitis, and epileptic patients with previously diagnosed pancreatitis should be monitored for development of hypertriglyceridemia.